The present invention relates to bags commonly used to contain and dispose of various items, and more particularly to bags having an integral closure system.
Bags, particularly flexible bags, are often made of comparatively inexpensive polymeric materials. Such bags have been widely employed for containment and/or disposal of various items and/or materials. As utilized herein, the term xe2x80x9cflexiblexe2x80x9d refers to materials which are capable of being flexed or bent, especially repeatedly, since they are compliant and yieldable in response to externally applied forces which ordinarily occur during the use of the bag. Accordingly, xe2x80x9cflexiblexe2x80x9d is substantially opposite in meaning to the terms xe2x80x9cinflexiblexe2x80x9d, xe2x80x9crigidxe2x80x9d or xe2x80x9cunyieldingxe2x80x9d in response to external forces normally occurring in use. Materials and structures which are flexible, therefore, may be altered in shape and structure to accommodate external forces and to conform to the shape of objects brought into contact with them without losing their integrity. For example, flexible bags may be used as liners for durable trash cans.
For purposes of storing or disposing of materials contained in flexible bags, several techniques to close the bag are known in the art. For example, twist ties have been commonly utilized. However, twist ties require a component separate from the trash bag, i.e., the twist tie itself. This separate component may become lost or accidentally discarded. Also, twist ties have not achieved great success in providing secure closure of bags.
Another technique known in the art is to use sinusoidally-shaped edges at the opening of the bag. These edges can be overlapped and tied together to form handles, as illustrated in U.S. Pat. No. 5,246,110, issued Sep. 21, 1993 to Greyvenstein. However, the sinusoidal edges which are to become the handles drape unevenly over the top of any durable container which the flexible bag may line. This provides an uneven and unsightly appearance while the flexible bag is in use. Furthermore, the stretch characteristics of the material forming the handle is typically equivalent to that forming the balance of the bag. This prevents the handles from preferentially straining during the tying procedure and providing a means of closing the bag which is easy to use.
Yet another technique known in the art is to provide a drawstring at the top circumference of the bag as illustrated in U.S. Pat. No. 4,778,283, issued Oct. 18, 1988 to Osborn. However, the drawstring closure is expensive and often rips in use.
Commonly assigned U.S. application Ser. No. 09/336,211, filed Jun. 18, 1999 in the name of Jackson, and Ser. No. 09/336,212, filed Jun. 18, 1999 in the name of Meyer et al., the disclosures of which are incorporated herein by reference, disclose flexible bags having closures. Specifically, drawstring-type closures, tyable handles or flaps, twist-tie or interlocking strip closures, adhesive-based closures, interlocking mechanical seals, removable ties, or strips made of bag composition, and heat seals are disclosed.
The present invention provides a closure for a flexible bag which is easy to use, integral with the bag, and utilizes preferred material properties of the bag.
The present invention is a bag having at least one sheet of flexible material assembled to form a semi-enclosed container. The container has an opening defined by a periphery. The bag has a fill direction generally perpendicular to the opening. The bag has a closure zone juxtaposed with the periphery. The closure includes a first region and a second region. The first region undergoes a substantially molecular-level deformation and the second region initially undergoes a substantially geometric deformation when the sheet of flexible material is subjected to applied tensile forces. The closure zone of the bag is extensible in the fill direction in response to such tensile forces. The tensile forces may be applied generally parallel to the fill direction. A knot, formed from portions of the closure zone, remains tied in response to forces applied to the knot.